The present invention relates to a power rectifier, and more particularly to such a power rectifier, which has means to protect the chip unit against the radiation of fusion and to stop the resin from an overflow during its fabrication.
FIG. 1 shows a power rectifier according to the prior art. This structure of power rectifier comprises a heat dissipation base 1' adapted for fastening to a heat sink, a hexagonal gasket 2' soldered to the top side of the heat dissipation base 1' around a flat, circular top projection of the heat dissipation base 1', a chip unit 3', the chip unit 3' comprising a chip 31' and two molybdenum pads 32' respectively disposed at top and bottom sides of the chip 31', a conducting rod member 4' soldered to the top-sided molybdenum pad of the chip unit 3', the conducting rod member 4' having a shank 42', and a cover shell 5' soldered to the hexagonal gasket 2' and covered over the chip unit 3' and the conducting rod member 4' after the molding of a resin on the top of the heat dissipation base 1' and the chip unit 3'. The cover shell 5' comprises a center tube 51', which receives the shank 42' of the conducting rod member 4'. The top end of the shank 42' is extended out of the center tube 51' of the cover shell 5' and processed to form an end contact. After the hexagonal gasket 2' and the heat dissipation base 1' have been soldered together, the topmost edge of the heat dissipation base 1' is disposed in flush with the top side wall of the hexagonal gasket 2'. It is difficult to hold the chip unit 3' on the smooth topmost edge of the heat dissipation base 1' when soldering the chip unit 3' to the heat dissipation base 1'. When molding the resin on the heat dissipation base 1' and the chip unit 3', the molten resin may flow out of the heat dissipation base 1' over the hexagonal gasket 2', affecting further procedure of soldering the cover shell 5' to the hexagonal gasket 2'. Before soldering the cover shell 5' to the hexagonal gasket 2', the overflow of the resin must be removed. Further, when soldering the cover shell 5' to the hexagonal gasket 2' the radiation of fusion may damages the chip 31' of the chip unit 3'.